Patent GB-643859-A (GB)
Title: Improvements in or relating to collagen strands and the manufacture thereof
IPC: D01F4/00
Filed: 1947-04-10
Abstract: <PICT:0643859/IV (a)/1> A collagen strand is stretched by passing it while in a softened state along an endless belt which is driven at a linear speed greater than that at which the strand is fed on to the belt.  The belt may be driven at a linear speed 15-40 per cent greater than that at which the strand is fed to it.  This stretching treatment may be preceded or followed by other treatments in which an endless band is used for conveying the strand.  The term "strand" includes a filament, thread or tape.  Single or multiple filament strands may be treated.  A substantially unitary strand resulting from twisting together a number of wet untanned filaments, so that they coalesce, may be treated.  The strand may be a soft, newly spun strand as removed from a spinning bath.  Treating liquid may be directed along the entire length of the strand.  Two or more belts in series, each imparting a portion of the total stretch may be provided.  As shown, a collagen strand is unwound from a spool 8 and passed over a guide roll 3 to the endless belt 1, and is subsequently wound up on roll 10. Treating liquid is directed on to the strand by jets 5.  The belt is driven independently of the supply and take-up spools.  A collagen solution may be obtained by dissolving cleaned corium of hide or skin in formic or other organic acid.  The solution is extruded into a solution of ammonium sulphate containing 35 per cent or more of the salt and maintained at pH 7.8 and 20-30 DEG  C. Sodium sulphate, magnesium sulphate, ethyl alcohol, acetone, diacetone alcohol, or ethylene glycol ethyl ether, may be used instead of ammonium sulphate for coagulating the collagen solution. The strand produced is removed from the coagulating bath and directed on to an endless belt which is preferably run at a speed to remove the strand from the bath without applying undue tension.  The linear speed of the take-up spool for the strand as it leaves this belt is greater than that of the belt, e.g. 100 per cent greater, so that the strand is stretched.  If desired, a spool may be interposed between the bath and the belt which is operated at a greater speed than the spool so as to produce stretching of the strand.  The spooled stretched strand is preferably left in contact with the coagulating solution until it is set in the stretched condition.  The strand may then be treated with a pre-tanning solution, e.g. a solution of formaldehyde or salt of iron, aluminium, or chromium, preferably containing a coagulant such as ammonium sulphate.  The strand as removed from the coagulating bath or after pre-stretching and other treatment is softened by treatment with water or an aqueous solution, e.g. of ammonium sulphate, and delivered to the endless belt travelling faster than the rate at which the strand is supplied to it so that the strand is stretched.  Softening liquid may be applied to the strand while it is travelling on the belt.  The strand may then be subjected to a final tanning treatment and then washed and dried. The strand may be subjected to the tanning treatments and to the washing treatment while passing through a travelling belt apparatus. For these treatments, the linear speeds of the unwinding spool, the belt, and the winding spool, may be made equal so that there is no stretching.  The strand may be used for making surgical sutures.ALSO:Sutures are made from threads, filaments, strands, tapes, or the like of collagen which have been subjected to a stretching operation to impart increased tensile strength.  Single or multiple filament strands may be used.  A substantially unitary strand resulting from twisting together a number of wet untanned filaments so that they coalesce may be subjected to the stretching operation.  A collagen filament may be obtained by extruding a solution in formic or other organic acid of cleaned corium of hide or skin into a coagulating liquid.  The filament, thread, or the like may be subjected to tanning with solutions of formaldehyde or salts of iron, chromium or aluminium.